Dynamic Polarization Modulation and Control

ABSTRACT

A method for sending a data from an electromagnetic radiator by polarization modulation of an electromagnetic wave includes radiating from the radiator first and second electromagnetic waves including first and second polarizations respectively, the first polarization being different than the second polarization. The first and second electromagnetic waves form a third electromagnetic wave having a third polarization different from the first or second polarization. The method includes modulating the third polarization responsive to the data by modulating one or more parts of the third electromagnetic wave. The data is sent in the third polarization. A system for sending a data includes an oscillator adapted to generate an oscillating signal, and a phase shifter coupled to the oscillator and adapted to generate a first phase-shifted oscillating signal having a first phase. The phase shifter is adapted to vary the phase difference across a predefined range in response to the data.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit under 35 §U.S.C 119(e) ofU.S. Provisional Patent Application No. 61/600,493, filed Feb. 17, 2012,entitled “DYNAMIC POLARIZATION MODULATION AND CONTROL” and ProvisionalPatent Application No. 61/705,996, filed Sep. 26, 2012, entitled“POLARIZATION AGILE TRANSMITTER & RECEIVER ARCHITECTURE”, the content ofwhich are incorporated herein by reference in their entirety. Thepresent application is related to U.S. patent application Ser. No.13/654,420, filed Oct. 18, 2012, entitled “EFFICIENT ACTIVE MULTI-DRIVERADIATOR”, the content of which is incorporated herein by reference inits entirety.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSOREDRESEARCH AND DEVELOPMENT

This invention was made with government support under FA8650-09-C-7924awarded by USAF/ESC. The government has certain rights in the invention.

BACKGROUND

The present invention relates generally to sending data byelectromagnetic (EM) waves and in particular, to sending data throughpolarization modulation of electromagnetic waves.

The rise in use of the EM-spectrum has created a great demand to usethat limited spectrum more efficiently, and with enhanced security.Advances in data processing and information theory help, but there isroom for improvement on the hardware side. Amplitude modulation (AM)uses a low frequency data signal, such as a human voice, to modulate theamplitude a much higher constant frequency carrier signal to form theradiated EM transmission wave. Alternatively, frequency modulation (FM)uses the low frequency data to modulate the frequency of a much higherfrequency carrier signal of constant amplitude to form the radiated EMtransmission wave.

While most modern radios make use of both in phase (I) and quadrature(Q) signals, i.e. two independent data streams, they do not takeadvantage of the additional throughput offered by using multiplepolarizations. This is because often the orientation of the receiveantenna is not known and thus signals are sent with a singlepolarization (either circular or linear).

Polarization is a property of some radiated EM waves. Polarizationexamples include linear or plane, elliptical, and circular. Polarizationof transmitted signals is used to enhance transmission characteristicsof radio waves, i.e. by polarizing a radiated EM wave to match theorientation of a receiving antenna (hereinafter alternatively referredto as receive antenna or receiver). Because the orientation of thereceiver is unknown, sending data from a sending antenna (hereinafteralternatively referred to as radiating antenna or radiator ortransmitter) in a circular polarization either clockwise (CW) orcounterclockwise (CCW) is more effective than linear polarizationsbecause the receiver can rotate in the x-y plane without effect on thesignals and the degradation due to the receiver being off axis to thez-axis is similar to that of linear polarizations.

Polarization multiplexing is used in the optical regime where twodifferent light beams, one with CW circular polarization and anotherwith CCW circular polarization are combined and sent over an opticalfiber transmission line at the same time to double the available signalbandwidth. This is possible because the orientation of the opticalreceiver is known in comparison to the fiber orientation so that the twodifferently polarized optical signals can be separated and each treatedindividually as separate signal transmission paths. In most casesantennas are single-port antennas capable of transmitting or receivingonly a specific type of polarization.

BRIEF SUMMARY

According to one embodiment of the present invention, a method forsending a data from an electromagnetic radiator by polarizationmodulation of an electromagnetic wave includes radiating from theradiator a first electromagnetic wave including a first polarization,and radiating from the radiator a second electromagnetic wave includinga second polarization different than the first polarization. The firstand second electromagnetic waves form a third electromagnetic wavehaving a third polarization different from the first or secondpolarization. The method further includes modulating the thirdpolarization responsive to the data by modulating one or more parts ofthe third electromagnetic wave. The data is sent in the thirdpolarization.

According to one embodiment, the first electromagnetic wave includes afirst phase and the second electromagnetic wave includes a second phase.The one or more parts are selected from the group consisting of thefirst phase, and the second phase. According to one embodiment, thefirst electromagnetic wave includes a first amplitude and the secondelectromagnetic wave includes a second amplitude. The one or more partsare selected from the group consisting of the first amplitude, and thesecond amplitude.

According to one embodiment, the first electromagnetic wave includes afirst phase and a first amplitude and the second electromagnetic waveincludes a second phase and a second amplitude. The one or more partsare selected from the group consisting of the first phase, the secondphase, the first amplitude, and the second amplitude. According to oneembodiment, the first electromagnetic wave includes a first phase and afirst amplitude and the second electromagnetic wave includes a secondphase and a second amplitude. Modulating one or more parts includessimultaneously modulating the first phase, the second phase, the firstamplitude, and the second amplitude.

According to one embodiment, the method further includes setting thefirst polarization to a clock-wise circular polarization, and settingthe second polarization to a counter-clock-wise circular polarization.According to one embodiment, the method further includes setting thefirst polarization to a first linear polarization having a first angle,and setting the second polarization to a second linear polarizationhaving a second angle substantially perpendicular to the first angle.According to one embodiment, the third polarization is a linearpolarization. According to one embodiment, the third polarization is anelliptical polarization.

According to one embodiment, the method further includes setting a firstamplitude of the first electromagnetic wave equal to a second amplitudeof the second electromagnetic wave, setting the first polarization to aclock-wise circular polarization, and setting the second polarization toa counter-clock-wise circular polarization. The one or more partsincludes a first phase of the first electromagnetic wave and a secondphase of the second electromagnetic wave, the third polarization being alinear polarization having an angle. The method further includesmodulating the angle responsive to a difference between the first andsecond phase, the difference being responsive to the data. According toone embodiment, the angle corresponds to a symbol representing the data.According to one embodiment, the symbol sends a single bit ofinformation at a time. According to one embodiment, the symbol sends amultitude of bits of data simultaneously in time.

According to one embodiment, the method further includes setting a firstphase of the first electromagnetic wave equal to a second phase of thesecond electromagnetic wave, setting the first polarization to aclock-wise circular polarization, and setting the second polarization toa counter-clock-wise circular polarization. The one or more partsincludes a first amplitude of the first electromagnetic wave and asecond amplitude of the second electromagnetic wave, the thirdpolarization being an elliptical polarization having a polarizationratio. The method further includes modulating the polarization ratioresponsive to the data.

According to one embodiment, the polarization ratio is a quotient of thefirst amplitude divided by the second amplitude. According to oneembodiment, the polarization ratio corresponds to a symbol representingthe data.

According to one embodiment of the present invention, a method forreceiving a data from an electromagnetic receiver by polarizationdemodulation of an electromagnetic wave, the method includes receivingfrom an antenna a first signal having a first polarization and a secondsignal having a second polarization, the first and second signals beingassociated with the electromagnetic wave, the electromagnetic waveincluding a third polarization. The method further includes determiningan amplitude of the first signal, determining an amplitude of the secondsignal, and determining an angle of the third polarization to receivethe data.

According to one embodiment, the first and second polarizations arelinear. According to one embodiment, the first and second polarizationsare substantially orthogonal. According to one embodiment, determiningthe angle includes calculating a quotient of the amplitude of the secondsignal divided by the amplitude of the first signal.

According to one embodiment of the present invention, a system forsending a data from a radiator by polarization modulation of anelectromagnetic wave includes an oscillator adapted to generate anoscillating signal, and a phase shifter coupled to the oscillator andadapted to generate a first phase-shifted oscillating signal having afirst phase. A phase difference exists between the first phase and theoscillating signal. The phase shifter is further adapted to vary thephase difference across a predefined range in response to the data.

According to one embodiment, the phase shifter is further adapted togenerate a second phase-shifted oscillating signal having a secondphase. A phase difference between the first phase and the second phasedefines the phase difference.

According to one embodiment, the system further includes a radiatoradapted to accept the first phase-shifted oscillating signal and theoscillating signal and respectively radiate a first electromagnetic wavehaving a first circular polarization and a second electromagnetic wavehaving a second circular polarization different than the first circularpolarization, the first electromagnetic wave and the secondelectromagnetic wave adapted to form a third electromagnetic wave havinglinear polarization and having an angle, the angle being responsive tothe data.

According to one embodiment, the radiator includes an antenna positionedsubstantially in a plane defined by a first direction and a seconddirection orthogonal to the first direction, the antenna being symmetricabout a center in the first direction and in the second direction, theantenna including a first port positioned at an edge of the antenna inthe first direction and a second port positioned at an edge of theantenna in the second direction. According to one embodiment, theradiator includes a first antenna adapted to radiate the firstelectromagnetic wave and second antenna adapted to radiate the secondelectromagnetic wave.

According to one embodiment of the present invention, a system forsending a data from a radiator by polarization modulation of anelectromagnetic wave includes a first circuit adapted to generate afirst signal and a second signal, an oscillator adapted to generate anoscillating signal, a phase shifter coupled to the oscillator andadapted to generate a first phase-shifted oscillating signal and asecond phase-shifted oscillating signal having a phase differencetherebetween. The phase shifter is adapted to vary the phase differenceacross a predefined range in response to the data. The system furtherincludes a first frequency converter is coupled to the phase shifter andthe first circuit, the first frequency converter adapted to convert afrequency of the first signal in response to the first phase-shiftedoscillating signal to generate a first frequency converted signal, and asecond frequency converter coupled to the phase shifter and the firstcircuit, the second frequency converter adapted to convert a frequencyof the second signal in response to the second phase-shifted oscillatingsignal to generate a second frequency converted signal.

According to one embodiment, the system further includes a radiatoradapted to accept the first and second frequency converted signals andrespectively radiate a first electromagnetic wave having a firstpolarization and a second electromagnetic wave having a secondpolarization different than the first polarization, the firstelectromagnetic wave and the second electromagnetic wave adapted to forma third electromagnetic wave having a third polarization, the thirdpolarization modulated by one or more parts of the combinedelectromagnetic wave responsive to the data.

According to one embodiment, the first polarization is a clock-wisecircular polarization and the second polarization is acounter-clock-wise circular polarization. According to one embodiment,the first polarization is a first linear polarization having a firstangle and the second polarization is a second linear polarization havinga second angle substantially perpendicular to the first angle.

According to one embodiment, a first phase of the first electromagneticwave is equal to a second phase of the second electromagnetic wave, thefirst polarization is a clock-wise circular polarization, the secondpolarization is a counter-clock-wise circular polarization. The one ormore parts includes a first amplitude of the first electromagnetic waveand a second amplitude of the second electromagnetic wave, the thirdpolarization being an elliptical polarization having a polarizationratio responsive to the data.

According to one embodiment of the present invention, a system forreceiving a data from an electromagnetic wave by polarizationdemodulation includes an antenna adapted to pick up a first signalhaving a first polarization and a second signal having a secondpolarization, the first and second signals being associated with theelectromagnetic wave. The electromagnetic wave including a thirdpolarization, a first circuit adapted to determine an amplitude of thefirst signal, a second circuit adapted to determine an amplitude of thesecond signal, and a third circuit adapted to determine an angle of thethird polarization responsive to the data.

According to one embodiment, the third circuit is further adapted tocalculate a quotient of the amplitude of the second signal divided bythe amplitude of the first signal. The quotient is responsive to theangle.

A better understanding of the nature and advantages of the embodimentsof the present invention may be gained with reference to the followingdetailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified block diagram of a system for sending data from atransmitter to a receiver by polarization modulation of anelectromagnetic wave with a symbol encoded to a data bit ‘0’, inaccordance with an embodiment of the present invention.

FIG. 2 is a simplified block diagram of the system for sending datashown in FIG. 1 with a symbol encoded to a data bit ‘1’, in accordancewith an embodiment of the present invention.

FIG. 3 is a simplified block diagram of a system for sending data from atransmitter to a receiver by polarization modulation of anelectromagnetic wave with a symbol encoded to a data bit ‘00’, inaccordance with an embodiment of the present invention.

FIG. 4 is a simplified block diagram of the system for sending datashown in FIG. 3 with a symbol encoded to a data bit ‘01’, in accordancewith an embodiment of the present invention.

FIG. 5 is a simplified block diagram of the system for sending datashown in FIG. 3 with a symbol encoded to a data bit ‘10’, in accordancewith an embodiment of the present invention.

FIG. 6 is a simplified block diagram of the system for sending datashown in FIG. 3 with a symbol encoded to a data bit ‘11’, in accordancewith an embodiment of the present invention.

FIG. 7 is a simplified block diagram of a system for sending data from atransmitter to a receiver by polarization modulation of anelectromagnetic wave with a symbol being a polarization ratio encoded toa data bit ‘0’, in accordance with an embodiment of the presentinvention.

FIG. 8 is a simplified block diagram of the system for sending datashown in FIG. 7 with a symbol encoded to a data bit ‘0’, in accordancewith an embodiment of the present invention.

FIG. 9 is a simplified block diagram of a system for sending data from atransmitter to a receiver by polarization modulation of anelectromagnetic wave with a symbol being a polarization ratio encoded toa data bit ‘00’, in accordance with an embodiment of the presentinvention.

FIG. 10 is a simplified block diagram of the system for sending datashown in FIG. 9 with a symbol encoded to a data bit ‘01’, in accordancewith an embodiment of the present invention.

FIG. 11 is a simplified block diagram of the system for sending datashown in FIG. 9 with a symbol encoded to a data bit ‘10’, in accordancewith an embodiment of the present invention.

FIG. 12 is a simplified block diagram of the system for sending datashown in FIG. 9 with a symbol encoded to a data bit ‘11’, in accordancewith an embodiment of the present invention.

FIG. 13 is a simplified block diagram of a system for sending data froma transmitter to a receiver by polarization modulation of anelectromagnetic wave with a symbol being a polarization ratio and angleencoded to a data bit ‘00’, in accordance with an embodiment of thepresent invention.

FIG. 14 is a simplified block diagram of the system for sending datashown in FIG. 13 with a symbol encoded to a data bit ‘01’, in accordancewith an embodiment of the present invention.

FIG. 15 is a simplified block diagram of the system for sending datashown in FIG. 13 with a symbol encoded to a data bit ‘10’, in accordancewith an embodiment of the present invention.

FIG. 16 is a simplified block diagram of the system for sending datashown in FIG. 13 with a symbol encoded to a data bit ‘11’, in accordancewith an embodiment of the present invention.

FIG. 17 is a simplified block diagram of a radiator in perspective viewwith a multitude of active radiators, in accordance with an embodimentof the present invention.

FIG. 18 is a plot of the simulation results showing the full 180°polarization angle rotation is achievable by changing the relative phaseof the CW and CCW radiators shown in FIG. 17.

FIG. 19 is a plot of the simulation results showing the polarizationratio versus the relative phase of the CW and CCW radiators shown inFIG. 17 when a linear polarization is desired.

FIG. 20 is an exemplary flow chart for maintaining a polarization matchbetween a radiator and a receiving antenna, in accordance with anembodiment of the present invention.

FIG. 21 is a simplified perspective view of a radiator with twoorthogonal ports, in accordance with an embodiment of the presentinvention.

FIG. 22 is a simplified block diagram of a polarization agiletransmitter circuit, in accordance with an embodiment of the presentinvention.

FIG. 23 is a simplified block diagram of a polarization agile receivercircuit, in accordance with an embodiment of the present invention.

FIG. 24 is a simplified block diagram of a basic polarization agiletransmitter circuit, in accordance with an embodiment of the presentinvention.

DETAILED DESCRIPTION

Regardless of the information being sent, there are four independentdata streams that can be sent as long as the energy is being received inthe far-field region of the antennas. The far-field region of theantennas is where the presence of the receive antenna does not interferewith the send antenna and where the Poynting vector is parallel to theline connecting the two antennas and pointing toward the receiveantenna.

The four independent data streams result from the ability to sendinformation “in phase” (I) and “in quadrature” (Q), i.e. 90° separationin phase when down converting the signal, simultaneously for any givenpolarization independently. There are also two independent polarizationsthat can each support signals in phase and quadrature. Defining acoordinate system with the z-axis parallel to the Poynting vector, theE-field and H-field planes will lie in the x-y plane. The twoindependent polarizations can be defined with linear polarizations thatare 90° apart in the x-y plane, or with circular polarization in boththe CW and CCW directions.

According to an embodiment of the present invention, a method and systemis described whereby polarization modulation transmits or sends datathrough an EM wave. The term “polarization” is defined herein as thedirection of the electric field vector of a radiated EM wave, such as aradio wave. This definition is not to be confused with the term“polarization” used in the completely different context of dielectricmaterial properties, wherein the term polarization, i.e. “dielectricpolarization”, describes a process producing a relative displacement ofbound electrical charges in a material by applying an electric field.The term “polarization” is also used in another different context wherepolarization is related to an electrical polarity difference of anelectrical component, such as an electrical plug with “+” and “−”terminals or component polarization. Dielectric polarization andcomponent polarization have nothing to do with polarization in thecontext of a radiated EM wave, which is described herein.

Sending data by modulating the polarization provides a way to utilizeall four theoretically possible independent data streams simultaneouslywithout the drawback of one fixed polarization at the receiver. Further,according to another embodiment, sending data through polarizationmodulation adds an extra layer of security to the data transmissionbecause not only is the proper antenna and radio required on the receiveside, but the polarization in undesired directions may be different thanin the desired direction. Because the symbol is the polarization, thedata sent to the intended receiver in the desired direction is differentthan the data received in undesired directions. Polarization modulationis in stark contrast with traditional radio and antenna modulationschemes where the signal is attenuated in the undesired directions butcan still be recovered with a sensitive enough receiver. In other words,with polarization modulation the signal itself will change based on thelocation of the receiver, effectively attenuating and scrambling thesignal in undesirable directions. Using a phased array and proper designof the radiating structure, the transmitted EM beam can be steered tosend most of the power and the correct signal to different receivers atdifferent times.

FIG. 1 is a simplified block diagram of a communication system 100 forsending data from a transmitter 105 to a receiver 110 by polarizationmodulation of an EM wave 115 with a symbol S 120 encoded to a data bit‘0’, in accordance with an embodiment of the present invention.Transmitter 105 may simultaneously send out or radiate a first EM waveincluding a first polarization and a second EM wave including a secondpolarization different than the first polarization at a near fieldposition 125 of transmitter 105. The first and second EM waves combinethrough superposition to form a third EM wave at a far field position130 near receiver 110. The third EM wave may have a differentpolarization than either the first or second EM waves. By settingparameters or parts of the first and second EM waves appropriately, thepolarization of the third EM wave in the far field is modulatedresponsive to data being sent or transmitted.

According to an embodiment of the invention, two circularly polarized EMwaves are radiated by a transmitter with the same amplitude butdifferent circular polarizations, one with CW and the other with CCWcircular polarizations. The resulting effect in the far field is alinearly polarized EM wave at a field angle, which is determined by therelative phase difference between the two EM waves as described below.By modulating the phases of the two circularly polarized fields, theangle of the linear polarization that is produced in the far field ismodulated. Further, data may be encoded with the angle position being asymbol and the information transmitted by polarization modulation of theEM waves.

The EM wave and its polarization are characterized by describing itselectrical field vector represented in a plane defined by a X-axis 135and a Y-axis 140 at time t=0. The Z-axis in a direction out of the pagerepresents the direction of the Poynting vector of the EM wave andcorresponds to the direction of propagation.

In one embodiment the first EM wave is represented at near field 125 byits electrical field vector E₁ positioned on X-axis 135 at t=0. Thisfirst EM wave includes CW polarization, which is represented by thesmall dashed directional circle 150, with small arrows indicating theposition of E₁ will change at t>0 by rotating the point of E₁ in a CWdirection relative to the previous time, while the base of E₁ remainsfixed at the origin of X-axis 135 and a Y-axis 140. The length of vectorE₁ corresponds to an amplitude A of the first EM wave. The first EM wavemay be represented mathematically in terms of unit vectors u_(x) andu_(y) by the equation:

E ₁ =A(cos(ωt+φ ₁)u _(x)+cos(ωt+φ ₁+π/2)u _(y))  (Eq. 1),

where ω represents the angular frequency, and the phase φ₁=0° since E₁is positioned or aligned on X-axis 135 at t=0.

As a matter of notation, phase is used to represent the phase of thesignal in time and angle to represent the physical angle of the fieldpolarization in space. It is understood, the first EM wave could besimilarly represented by sin functions. However, sin functions referencethe electric field vector angle relative to the Y-axis. The cosfunction, used herein, provides a simpler explanation by insteadreferencing the vector angle to the X-axis, however mathematicalderivations using sin functions are analogous.

The second EM wave in near field 125 is represented by its electricalfield vector E₂ positioned the X-axis at t=0. However, the second EMwave includes CCW polarization, which is represented by the small dashedcircle 155, with small arrows indicating the position of E₂ will changeat t>0 by rotating the point of E₂ in a CCW direction relative to theprevious time, while the base of E₂ remains fixed at the origin of theX-axis and a the Y-axis. The second EM wave, having the same amplitude Aas the first EM wave, may be similarly represented mathematically interms of unit vectors u_(x) and u_(y) by the equation:

E ₂ =A(cos(ωt+φ ₂)u _(x)+cos(ωt+φ ₂−π/2)u _(y))  (Eq. 2),

where ω represents the angular frequency, and the phase φ₂=0° since E₂is positioned or aligned on X-axis 135 at t=0. The polarizationdirection is represented in equations 1 and 2 by the + or − sign beforethe π/2 corresponding to CW and CCW respectively.

Combining the first and second EM waves in far field 130 gives the thirdEM wave E_(t) as follows:

E _(t) =E ₁ +E ₂  (Eq. 3).

Substituting from equations 1 and 2 into equation 3 yields:

E _(t) =A(cos(ωt+φ ₁)u _(x)+cos(ωt+φ ₁+π/2)u _(y))+A(cos(ωt+φ ₂)u_(x)+cos(ωt+φ ₂−π/2)u _(y))  (Eq. 4).

Define:

Δφ=φ₁−φ₂  (Eq. 5), and

Σφ=φ₁+φ₂  (Eq. 6).

Substitution of equations 5 and 6 into equation 4 yields:

E _(t)=2A[cos(Δφ/2)cos(ωt+Σφ/2)u _(x)+cos(Δφ/2+π/2)cos(ωt+Σφ/2)u_(y)]  (Eq. 7).

Rewriting equation 7 by collecting the vector components yields:

E _(t)=2A{cos(ωt+Σφ/2)[cos(Δφ/2)u _(x)+cos(Δφ/2+π/2)u _(y)]}  (Eq. 8).

Removing the π/2 term in equation 8 by replacing the cos function by asin function yields:

E _(t)=2A{cos(ωt+Σφ/2)[cos(Δφ/2)u _(x)−sin(Δφ/2)u _(y)]}  (Eq. 9).

Equation 9 describes the resulting superposition of the first and secondEM waves at far field 130. It should be recognized that equation 9includes the time varying part of the field at the left part of theequation and the vector directional components at the right. Thus, thevector directional components of E_(t) in the x and y dimensions arealways in phase regardless of φ₁ or φ_(z) and describe a linearlypolarized wave in far field. Equation 9 shows that the third field,E_(t), is characterized by:

mag(E _(t))=2A  (Eq. 10),

phase(E _(t))=Σφ/2  (Eq. 11), and

angle(E _(t))=−Δφ/2  (Eq. 12).

It is observed that; i) the magnitude of the third EM wave is alsoindependent of φ₁ or φ₂, and ii) the angle of polarization of the thirdEM wave is only dependent on the difference between the phases of theoriginal first and second EM waves. Thus, by modulating that relativephase (Δφ), the angle of the linear polarization in the far field willchange. This adds an additional level of security, as most currentreceivers are not even able to detect information transmitted in thisway, as they will only detect one polarization.

Using even and odd mode analysis, odd mode phase modulation (Δφ/2)between the first and second EM waves may modulate the angle of thepolarization of the third EM wave, while the even mode amplitude (A) andphase modulation (Σφ/2) will modulate the amplitude and phase of thereceived signal in a traditional sense at whatever polarization isdefined by the odd mode. Thus, even mode modulation can be used eitherto send additional data, for instance as conventional I(t) and Q(t)quadrature carrier signals in the time varying component of the third EMwave, or even to obscure the data symbol sent through the polarizationmodulation. This is because the polarization modulation signal is sentthrough Δφ, so changes to A and Σφ will not affect the intendedpolarization modulation symbol, but will change the phase and amplitudereceived by a traditional single polarization receiver. In contrast, bysending additional data symbols through the amplitudes of E₁ and E₂, aswell as through Σφ, all four theoretically independent data streams maybe used simultaneously.

Referring again to FIG. 1, the communication symbol for communicationsystem 100 is the polarization of the third EM wave. The symbol isencoded or modulated by setting one or more parts of the first andsecond EM waves by transmitter 105 to modulate the polarization receivedat receiver 110. The one or more parts of the first and second EM wavesinclude the phase and amplitude of the first EM wave and the phase andamplitude of the second EM wave.

When the amplitude of the first and second EM waves are set equal, i.e.the length of E₁ equals the length of E₂ as shown, then the third EMwave (E_(t)) at far field 130 is linearly polarized as mathematicallyderived in the equations above. Linear polarization is represented byshowing E_(t) without any directional circle 150 or 155. Unlike thecircular polarization for E₁ and E₂, E_(t) oscillates in time in theplane perpendicular to the X-Y plane intersecting the coordinate originat an angle θ with respect to the X-axis.

In this example symbol S 120 is the polarization angle θ of the thirdwave, E_(t). For example, S may be chosen equal to a data bit ‘0’ andmay be encoded to mean angle θ=0° by setting φ₁=φ₂=0° in transmitter105. Then, E_(t) will oscillate as a linear or plane polarized waveeither towards the + or −X axis directions in this case since the planeit oscillates in intersects the x-axis because angle θ=0°. Thus, E_(t)is shown with its vector pointing towards the +X axis direction at t=0.The magnitude of E_(t)=2A. The symbol may be decoded or demodulated atreceiver 110 by extracting the polarization angle as will be discussedin detail below.

FIG. 2 is a simplified block diagram of system 100 for sending datashown in FIG. 1 with symbol S 120 encoded to a data bit ‘1’, inaccordance with an embodiment of the present invention. FIG. 2 is markedwith the same features as FIG. 1 except S may be chosen equal to a databit ‘1’ and may be encoded to mean polarization angle θ=−90° by settingφ₁=+90° and φ₂=−90° in transmitter 105. It is noted that now E₂ is shownpointing downwards towards the −Y axis direction because φ₂=−90° issimilar to going back in time from t=0 against the CCW direction by 90°.

Thus FIG. 1 and FIG. 2 show a system where S is encoded for one bit datatransmission. However, because angle θ is determined from φ₁ and φ₂,which are analog parameters, angle θ may be continuously variable asdesired. According to an embodiment, the polarization angle θ of thethird EM wave may be varied in analog fashion to any desired angleacross a predefined range. Thus, encoding more than two angles providesa way to encode and simultaneously transmit a multitude of bitssimultaneously as described below.

FIG. 3 is a simplified block diagram of a system 300 for sending datafrom a transmitter 305 to a receiver 310 by polarization modulation ofan electromagnetic wave 315 with a symbol S 320 encoded to a data bit‘00’, in accordance with an embodiment of the present invention. FIG. 3is similar to the embodiment shown in FIG. 1 except in FIG. 3 symbol Sis encoded with two bits ‘00’ by setting φ₁=+90° and φ₂=−90° intransmitter 105, which results in polarization angle θ=0°. The symbolmay be decoded or demodulated at receiver 310 by extracting thepolarization.

FIG. 4 is a simplified block diagram of system 300 for sending datashown in FIG. 3 with symbol S 320 encoded to a data bit ‘01’, inaccordance with an embodiment of the present invention. FIG. 4 issimilar to the embodiment shown in FIG. 3 except in FIG. 4 symbol S isencoded with ‘01’ by setting φ₁=+45° and φ₂=−45° in transmitter 305which results in polarization angle θ=−45°. Then, E_(t) will oscillateas a linear or plane polarized wave in the plane perpendicular to theX-Y plane at angle θ=−45° relative to the X-axis.

FIG. 5 is a simplified block diagram of system 300 for sending datashown in FIG. 3 with symbol S 320 encoded to a data bit ‘10’, inaccordance with an embodiment of the present invention. FIG. 5 issimilar to the embodiment shown in FIG. 3 except in FIG. 5 symbol S isencoded with ‘10’ by setting φ₁=+90° and φ₂=−90° in transmitter 305which results in polarization angle θ=−90°. Then, E_(t) will oscillateas a linear or plane polarized wave in the plane perpendicular to theX-Y plane at angle θ=−90° relative to the X-axis, i.e. in the Y-axisdirection.

FIG. 6 is a simplified block diagram of system 300 for sending datashown in FIG. 3 with symbol S 320 encoded to a data bit ‘11’, inaccordance with an embodiment of the present invention. FIG. 6 issimilar to the embodiment shown in FIG. 3 except in FIG. 5 symbol S isencoded with ‘11’ by setting φ₁=+135° and φ₂=−135° in transmitter 305which results in polarization angle θ=−135°. Then, E_(t) will oscillateas a linear or plane polarized wave in the plane perpendicular to theX-Y plane at angle θ=−135° relative to the X-axis.

According to another embodiment, amplitude modulation of E₁ and E₂ maybe used on the odd mode to modulate the polarization of E_(t), which mayno longer be linear polarized, but rather E_(t) may be ellipticallypolarized, or if one amplitude is 0 and the other amplitude is non-zero,the result may be a circular polarization in the far field for E_(t).This means that data may also be sent by modulating the odd modeamplitude and by detecting the polarization ratio (polRatio) of E_(t),defined as the |E-field(CW)|/|E-field(CCW)|. From equations 1 and 2, Ais now defined separately for each EM wave E₁ and E₂ as:

E ₁ =A ₁(cos(ωt+φ ₁)u _(x)+cos(ωt+φ ₁+π/2)u _(y))  (Eq. 13), and

E ₂ =A ₂(cos(ωt+φ ₂)u _(x)+cos(ωt+φ ₂−π/2)u _(y))  (Eq. 14).

Thus, polRatio(E _(t))=A ₁ /A ₂  (Eq. 15).

A polarization ratio value near 1 is linearly polarized, while a valuenear 0 or very high indicates polarization closer to circular, i.e. withpolarization ratio=0 or infinity indicating exactly circularpolarization. For polarization ratio>1, the polarization of E_(t) may bea CW elliptical polarization, while for polarization ratio<1, thepolarization of E_(t) may be a CCW elliptical polarization. Theangle(E_(t)) of equation 12 now represents the angle of the major axisof the ellipse (or angle of linear polarization when A₁=A₂) and willstill equal −Δφ/2. Thus, as with independent data sent through CW or CCWcircular polarizations, there are 4 independent data streams that can besent (or I Q) modulation, allowing for full utilization of the availableEM bandwidth.

FIG. 7 is a simplified block diagram of a system 700 for sending datafrom a transmitter 705 to a receiver 710 by polarization modulation ofan electromagnetic wave 715 with a symbol S 720 being a polarizationratio encoded to a data bit ‘0’, in accordance with an embodiment of thepresent invention. FIG. 7 is similar to the embodiment shown in FIG. 1except in FIG. 7 symbol S 720 may be encoded by setting A₁=0 and A₂=1and by setting φ₁=φ₂=0° in transmitter 505, which results in apolRatio(E_(t))=0. Because A₁=0, E₁=0 and its vector representation isshown accordingly. The resulting E_(t) at the far field is a wave withCCW circular polarization 755.

FIG. 8 is a simplified block diagram of system 700 for sending datashown in FIG. 7 with symbol S 720 encoded to a data bit ‘1’, inaccordance with an embodiment of the present invention. FIG. 8 is markedwith the same features as FIG. 1 except symbol S 720 may be encoded bysetting A₁=A₂=1 and by setting φ₁=φ₂=0° in transmitter 705, whichresults in a polRatio(E_(t))=1. The resulting E_(t) at the far field isa wave with linear polarization analogous to the embodiment described inreference to FIG. 1.

FIG. 9 is a simplified block diagram of a system 900 for sending datafrom a transmitter to a receiver by polarization modulation of anelectromagnetic wave 915 with symbol S 920 being a polarization ratioencoded to a data bit ‘01’, in accordance with an embodiment of thepresent invention. In this embodiment two bits may be transmittedsimultaneously by modulating the polarization ratio. FIG. 9 is similarto the embodiment shown in FIG. 7 except in FIG. 9 symbol S 920 isencoded with two bits ‘00’.

FIG. 10 is a simplified block diagram of system 900 for sending datashown in FIG. 9 with symbol S 920 encoded to a data bit ‘01’, inaccordance with an embodiment of the present invention. FIG. 10 ismarked with the same features as FIG. 9 except symbol S 920 may beencoded by setting A₁=½ and A₂=1 and by setting φ₁=φ₂=0° in transmitter905, which results in a polRatio(E_(t))=½. The resulting E_(t) at thefar field is a wave with CCW elliptical polarization 1055 with majoraxis positioned along the X-axis.

FIG. 11 is a simplified block diagram of system 900 for sending datashown in FIG. 9 with a symbol encoded to a data bit ‘10’, in accordancewith an embodiment of the present invention. FIG. 11 is marked with thesame features as FIG. 1 except symbol S 920 may be encoded by settingA₁=A₂=1 and by setting φ₁=φ₂=0° in transmitter 905, which results in apolRatio(E_(t))=1. The resulting E_(t) at the far field is a wave withlinear polarization analogous to the embodiment described in referenceto FIG. 1.

FIG. 12 is a simplified block diagram of the system 900 for sending datashown in FIG. 9 with symbol S 920 encoded to a data bit ‘11’, inaccordance with an embodiment of the present invention. FIG. 12 ismarked with the same features as FIG. 9 except symbol S 920 may beencoded by setting A₁=1 and A₂=½ and by setting φ₁=φ₂=0° in transmitter905, which results in a polRatio(E_(t))=2. The resulting E_(t) at thefar field is a wave with CW elliptical polarization 1255 with major axispositioned along the X-axis.

FIG. 13 is a simplified block diagram of a system 1300 for sending datafrom a transmitter 1305 to a receiver 1310 by polarization modulation ofan electromagnetic wave 1315 with a symbol S 1320 being a polarizationangle and ratio encoded to a data bit ‘00’, in accordance with anembodiment of the present invention. The polarization angle andpolarization ratio are independently controlled and can be used incombination to define data encoding. FIG. 13 is marked with the samefeatures as FIG. 10 except symbol S 1320 may be encoded for data ‘00’.

FIG. 14 is a simplified block diagram of system 1300 for sending datashown in FIG. 13 with symbol S 1320 encoded to a data bit ‘01’, inaccordance with an embodiment of the present invention. FIG. 14 ismarked with the same features as FIG. 13 except symbol S 1320 may beencoded by setting A₁=½ and A₂=1 and by setting φ₁=+90° and φ₂=−90° intransmitter 1305, which results in a polRatio(E_(t))=½ andangle(E_(t))=−90°. The resulting E_(t) at the far field is a wave withCCW elliptical polarization 1455 with major axis positioned along theY-axis, i.e. angle from the X-axis=−90°.

FIG. 15 is a simplified block diagram of system 1300 for sending datashown in FIG. 13 with symbol S 1320 encoded to a data bit ‘10’, inaccordance with an embodiment of the present invention. FIG. 15 ismarked with the same features as FIG. 12 except symbol S 1320 may beencoded for data ‘10’.

FIG. 16 is a simplified block diagram of system 1300 for sending datashown in FIG. 13 with symbol S 1320 encoded to a data bit ‘11’, inaccordance with an embodiment of the present invention. FIG. 16 ismarked with the same features as FIG. 14 except symbol S 1320 may beencoded by setting A₁=1 and A₂=½ and by setting φ₁=+90° and φ₂=−90° intransmitter 1305, which results in a polRatio(E_(t))=2 andangle(E_(t))=−90°. The resulting E_(t) at the far field is a wave withCW elliptical polarization 1655 with major axis positioned along theY-axis, i.e. angle from the X-axis=−90°.

According to an embodiment of the present invention, a system with twolinearly polarized waves that have 90° separation in polarization, i.e.the two linearly polarized waves are substantially orthogonal to eachother. The analysis of these linear polarized waves is the same as aboveonce the circularly polarized waves are broken down into Ex and Eyfields. Thus, if the waves are in phase, the far field signal will havelinear polarization, and the relative amplitudes of the two waves willchange the orientation of the polarization and the magnitude of thesignal on it. By changing their odd mode phase, the circularpolarization ratio will change, and by modulating their even mode phasewill modulate the phase in the far field.

FIG. 17 is a simplified block diagram of a polarization modulatingradiator 1700 in perspective view with a multitude of radiators, inaccordance with an embodiment of the present invention, including anantenna 1710 adapted to radiate the first EM wave with CW circularpolarization and second antenna 1720 adapted to radiate the second EMwave with CCW circular polarization. These individual radiators may beimplemented by driving a traveling wave around a loop, such as with anactive multi-drive radiator described in U.S. patent application Ser.No. 13/654,420, “EFFICIENT ACTIVE MULTI-DRIVE RADIATOR”, referencedabove. Each active multi-drive radiator operates by placing differentialamplifier ports 1730 around are ring that are feed by input feeds from acentral oscillator. The oscillator sends power at evenly spaced phasesdown each input feed, creating a traveling current wave around the loopand producing circularly polarized EM radiation.

The polarization direction (CW or CCW) is determined by a centraloscillator A and a central oscillator B in antennas 1710 and 1720respectively, and thus these two antennas can be implemented withopposite polarization directions. Central oscillator A and a centraloscillator B can then be locked to each other, and by changing the delayin the locking mechanisms, the relative phase between antennas 1710 and1720 can be varied and modulated. The amplitudes of the first EM waveand second EM wave with CCW can be adjusted by changing the gain of thedifferential amplifiers around the rings through their bias or throughother means. Thus full amplitude and phase control of the two radiatorsis achieved, and through the process described above, modulation of thefar field polarization is achieved.

FIG. 18 is a plot of the simulation results showing the full 180°polarization angle rotation is achievable by changing the relative phaseof the CW and CCW radiators shown in FIG. 17. FIG. 18 shows the linearpolarization angle of E_(t) on the Y-axis of the plot versus the phaseoffset Δφ between the radiators from 0 to 360 degrees on the X-axis ofthe plot. FIG. 18 is a plot of the simulation results showing thepolarization ratio of E_(t) versus the relative phase of the CW and CCWradiators shown in FIG. 17 when a linear polarization, i.e.polRatio(E_(t))=1, is desired. FIG. 18 shows the polarization ratio ofE_(t) on the Y-axis of the plot and the phase offset Δφ between theradiators from 0 to 360 degrees on the X-axis of the plot and that thepolRatio(E_(t)) stays in a range between about 0.9 and 1.13 as desired.

Polarization modulating radiator 1700 described above may be considereda single unit of a phased array of such radiators implemented toincrease the radiated gain of the system and to allow for beam steering.A phased array of such radiators will also allow for higher overallpower by utilizing power combining in the air. The angle of the beamsteering will be determined by the relative phase difference betweendifferent units of radiators, in the traditional phased array way, whilethe relative phase between radiators in the same unit will stilldetermine the angle of polarization.

According to one embodiment, the systems described above may beintegrated together on an integrated circuit. This provides for analogand digital controlling circuitry to be implemented on chip, a radiationsystem capable of beam steering, as well as polarization and signalmodulation in a compact integrated package.

Another embodiment of this invention is to use the system to dynamicallycontrol the polarization of signal (E_(t)). Rather than modulate thepolarization, the polarization can be set to a given optimum angle anddata can be transmitted in this linear polarization. If desired, due tochanging environmental or other conditions, the angle of thepolarization can be adjusted to maintain optimum performance in the formof power transfer to a receiver or other desired performance metric. Afeedback loop with the receiver is used, a polarization angle lockingscheme is used to maintain a maximum performance link betweentransmitter and receiver by always ensuring that the transmittedpolarization angle is one that supplies the optimum performance to thesystem.

The goal is to stay ‘polarization matched’ where the polarization of theincoming wave is matched to the polarization of the receive antenna, andthe receive antenna is able to receive a maximum amount of power. Forthis embodiment, the radiator is fixed in space, but is polarizationagile, such as the previous example polarization modulating radiator1700 with A₁=A₂=1 to produce a linear polarization of signal E_(t). Thereceive antenna is mobile in space, and has a linearly polarizedantenna. The receive antenna is also able to communicate back to thebase station with information about how much power it is receiving. Itshould be noted that the rudimentary algorithm described below to findthe maximum received power is only an example, and other 1 dimensionalsearch algorithms to find the maximum power received may also be used.

FIG. 19 is an exemplary flow chart 2000 for maintaining a polarizationmatch between a radiator and a receiving antenna, in accordance with anembodiment of the present invention. Assume at step 2100 that thesystem, i.e. system 300 described previously, starts in a state withpolarization mismatch between receiver 310 and transmitter 305. Thereceiver sends 2200 its received power information back to thetransmitter. By only adjusting the phase of the CW and CCW radiators,the transmitter rotates 2300 the linear polarization of the E_(t) wave asmall amount, i.e. 5 degrees, in a first direction. The receiver thenreports back 2400 the new received power information to the transmitter.

At step 2500, if the new power information is more than the previouspower information, repeat Step 2300 in the same direction; if the newpower information is less than the earlier power information, thepolarization angle of the E_(t) wave is changed a small amount in thedirection opposite the first direction of change. Over time the stepsize of the polarization angle change can also be decreased, i.e. lessthan 5 degrees, as the system gets closer to convergence. When aconvergence criterion, i.e. 100 loop iterations, is reached, record thereceived power as the maximum, and wait until receiver detectspolarization mismatch. At step 2600 the transmitter continues to monitorthe received power information from the receive antenna. If the receiveantenna is rotated, the power will drop due to polarization mismatch,and the receiver will tell the transmitter to start back at step 2200 toregain polarization match.

FIG. 21 is a simplified perspective view of a radiator 2100 with twoorthogonal ports, in accordance with an embodiment of the presentinvention. Radiator 2100 includes an patch antenna 2110 positionedsubstantially in a plane defined by a first direction 2120 and a seconddirection 2130 orthogonal to the first direction, the antenna beingsymmetric about a center 2140 in the first direction and in the seconddirection, the antenna including a first port 2150 positioned at an edge2160 of the antenna in the first direction and a second port 2170positioned at an edge 2180 of the antenna in the second direction.Incident linear 2185, circular 2190 and polarization modulated 2195fields are examples of fields that may be transmitted or received onradiator 2100.

Planar antennas can be integrated into IC manufacturing processes,leading to their popular use in modern wireless communication systems.In most cases such antennas are single-port antennas capable oftransmitting (receiving) only a specific type of polarization. Incontrast, radiator 2100 may transmit or receive simultaneously twopolarizations, which are orthogonal in space, thereby any desiredpolarization can be resolved into these orthogonal components. This canbe achieved using conventional antenna structures, i.e. a ring, patch,or slot, by adding an additional transmit (receive) port perpendicularto the existing main transmit (receive) port. It can be shown that thebehavior of each individual port of such a dual-port antenna isidentical to that of a single-port antenna corresponding to a givenpolarization. In other words, because the ports are oriented inorthogonal directions, they have no effect on each other.

FIG. 22 is a simplified block diagram of a polarization agiletransmitter circuit 2200, in accordance with an embodiment of thepresent invention, for sending a data from a radiator 2250 bypolarization modulation of an EM wave 2255. Polarization agiletransmitter circuit 2200 includes an optional baseband block 2205, anoptional first variable gain amplifier (VGA) 2210 coupled to a firstport of the optional baseband block 2205, and an optional second VGA2215 coupled to a second port of the optional baseband block 2205.Polarization agile transmitter circuit 2200 further includes a firstmixer or frequency converter 2220, a second mixer 2225, a localoscillator (LO) 2230, a variable phase shifter 2235, an optional firstpower amplifier (PA), and an optional second PA 2245.

The output of optional first VGA 2210 is input to first mixer 2220. Theoutput of optional second VGA 2215 is input to second mixer 2225. Localoscillator 2230 is adapted to generate an oscillating signal. Variablephase shifter 2235 is coupled to LO 2235. Variable phase shifter 2235 isadapted to generate a first phase-shifted oscillating signal and asecond phase-shifted oscillating signal. The first phase-shiftedoscillating signal and the second phase-shifted oscillating signal havea phase difference.

Unlike common phase shift circuits which may be set to a fixed phasedifference of 90°, variable phase shifter 2235 is further adapted tovary the phase difference across a predefined range in response to thedata. In other words, the phase difference may be set to any phasedifference in analog fashion—the predefined range set to particularphase differences as discussed in the sections above, for example, toencode data to a polarization angle used as a communication symbol ofthe EM wave 2255. The first mixer 2220 is coupled to variable phaseshifter 2235 and is adapted to convert a frequency of the first portsignal from optional baseband block 2205 in response to the firstphase-shifted oscillating signal to generate a first frequency convertedsignal. The second mixer 2225 is coupled to variable phase shifter 2235and is adapted to convert a frequency of the second port signal fromoptional baseband block 2205 in response to the second phase-shiftedoscillating signal to generate a second frequency converted signal.

The first frequency converted signal is input to optional first PA 2240.The second frequency converted signal is input to optional second PA2245. The outputs of optional first PA 2240 and optional second PA 2245may respectively drive the first and second antenna ports 2150 and 2170referenced in FIG. 21 or may respectively drive radiators A and Breferenced in FIG. 17 above.

FIG. 22 represents one embodiment for the polarization agile transmittershowing two parallel paths. The theory of operation for radiator 1700referenced in FIG. 17 will be discussed later, however the followingdiscussion will use radiator 2100 referenced in FIG. 21. Depending onwhether linear or circular polarization is desired, the variable phaseshifter may be set respectively to 0 degree or 90 degrees. The VGAs areindependently controlled at baseband and the outputs of the PAs feed thetwo orthogonal ports of radiator 2100. Operation of the transmittercircuit 2200 for different polarizations is discussed in the followingsections.

Linear Polarization: Generic Modulation

According to one embodiment, when desired, EM wave 2255 may be amodulated signal at one particular linear polarization. The phaseshifter is then set to 0 degrees, thus the two ports of radiator 2100are driven in phase. The base-band VGAs are adjusted to generate fieldsin the desired polarization. This is mathematically shown as follows.

Assume the desired linear polarization is to be oriented at an angle θwith respect to one of the transmit ports of radiator 2100. Themagnitude and phase are dependent upon which symbol is beingtransmitted. For example for constant envelope modulation schemes, E₀does not vary over time, but φ varies with the symbol.

The base band signals at the input to the VGAs are as follows:

V _(BB,port1) =V ₀·cos [(ω_(RF)−ω_(LO))t]  (Eq. 16), and

V _(BB,port2) =V ₀·cos [(ω_(RF)−ω_(LO))t]  (Eq. 17).

Depending on the direction of polarization, the VGA sets weights as cosθ & sin θ. Now the outputs of the VGAs become:

V _(BBVGA,port1) =V ₀·cos θ·cos [(ω_(RF)−ω_(LO))t]  (Eq. 18), and

V _(BBVGA,port2) =V ₀·sin θ·cos [(ω_(RF)−ω_(LO))t]  (Eq. 19).

Note that base-band VGA settings are held at fixed values for this case.

The up-converted signals will then be:

V _(port1) =V ₀·cos θ·cos(ω_(RF) t+φ)  (Eq. 20), and

V _(port2) =V ₀·sin θ·cos(ω_(RF) t+φ)  (Eq. 21),

where ω_(RF) is the RF carrier frequency (for simplicity, PA & mixergains are kept at unity).

When these two signals are fed to the two orthogonal ports of radiator2100, the signals combine in orthogonal directions in space, leading toan E-field vector at an angle,

tan⁻¹(Amp_(RF,port2)/Amp_(RF,port1))=tan⁻¹(sin θ/cos θ)=0  (Eq. 22)

The E-field already has the baseband magnitude information,

V ₀=[(Amp_(RF,port1) ²+Amp_(RF,port2) ²)]^(1/2)  (Eq. 23)

And phase information in the time domain.

As discussed above, the direction of linear polarization can be variedin many useful ways. For example, if the receiver is a generic 1-portreceiver, depending on its orientation, the transmitter can sweepthrough all possible VGA settings to find the optimum setting formaximum signal detection at the receiver. This also means that at thisoptimum setting, the receiver port is aligned with the incident E-fieldpolarization. Further, the base-band VGA settings can be varied at thesymbol rate to generate linear polarization modulation.

Linear Polarization: Polarization Modulation

In a polarization modulation scheme, according to one embodiment, themagnitude of the electric field vector (E₀), spatial orientation (θ) aswell as the phase (φ) can all vary depending on the symbol. A linearlypolarized input signal is modulated using the same dual port transmittercircuit 2200. Variable phase shifter 2235 is again kept at 0 degrees.Note that, it is impossible for a conventional single port antenna togenerate symbol dependent polarization as in the present embodiment.Similar to the previous case, the derivation follows equation 16 throughequation 23, however, in contrast to the previous embodiment, the VGAsettings can vary with the symbol. This means that cos θ and sin θ varywith the symbol and the angle varies at the symbol rate generatingpolarization modulation 2195 referenced in FIG. 21.

Circular Polarization

According to one embodiment, a circular polarization can similarly bedecomposed into two orthogonal components, which, contrary to the linearcase, are now in quadrature. The same transmitter circuit 2200architecture can be reused for generating circular polarization just bychanging variable phase shifter 2235 to 90 degrees.

Similar to the previous cases, the derivation follows equation 16through equation 17, however, in contrast to the previous embodiment,the VGA outputs are set at equal values for circular polarizationyielding:

V _(BBVGA,port1) =V ₀ ·A _(VGA)·cos [(ω_(RF)−ω_(LO))t]  (Eq. 24), and

V _(BBVGA,port2) =V ₀ ·A _(VGA)·sin [(ω_(RF)−ω_(LO))t]  (Eq. 25).

The up-converted signals will then be:

V _(port1) =V ₀ ·A _(VGA)·cos(ω_(RF) t+φ)  (Eq. 26), and

V _(port2) =V ₀ ·A _(VGA)·sin(ω_(RF) t+φ)  (Eq. 27),

where ω_(RF) is the RF carrier frequency (for simplicity, PA & mixergains are kept at unity). When these two signals are fed to the twoorthogonal ports of the transmit antenna 2100, the signals combine inorthogonal directions in space as well as in quadrature in time, leadingto a circular polarization 2190 referenced in FIG. 21.

Receiver Architecture

FIG. 23 is a simplified block diagram of a polarization agile receivercircuit 2300, in accordance with an embodiment of the present invention,for receiving a data from a radiator 2350 by polarization modulation ofan EM wave 2355. Polarization agile receiver circuit 2300 includes anoptional baseband block 2305, an optional first VGA 2310 coupled to afirst input port of the optional baseband block 2305, and an optionalsecond VGA 2315 coupled to a second input port of the optional basebandblock 2305. Polarization agile receiver circuit 2300 further includes afirst mixer or frequency converter 2320, a second mixer 2325, a LO 2330,an optional first low noise amplifier (LNA), and an optional second LNA2345.

Optional first VGA 2310 takes its input from the output of first mixer2320. Optional second VGA 2315 takes its input from the output of secondmixer 2325. Local oscillator 2330 is adapted to generate an oscillatingsignal. The first mixer 2320 is coupled to LO 2330 and is adapted todown convert a frequency of the first pick-up port signal from optionalfirst LNA 2340 in response to the oscillating signal to generate a firstfrequency converted signal. The second mixer 2325 is coupled to LO 2330and is adapted to down convert a frequency of the second pick-up portsignal from optional second LNA 2345 in response to the oscillatingsignal to generate a second frequency converted signal.

The first frequency converted signal is input to optional first VGA2310. The second frequency converted signal is input to optional secondVGA 2315. The inputs of the optional first and second LNA mayrespectively pick-up the signals generated at first and second antennaports 2150 and 2170 referenced in FIG. 21 or may respectively pick-upthe signals generated at radiators A and B referenced in FIG. 17 above.

Linear Polarization: Generic Modulation

When a linear polarization at an arbitrary angle is incident upon asingle port antenna, the antenna receives only a component of theincident field, which is aligned with the port of the antenna. Thisleads to reduced signal strength as well as orientation dependentsignal.

When such a polarization is incident on the dual-port antenna 2100referenced in FIG. 21, each port receives a part of the incident fieldand thus, contrary to the conventional single-port antenna, no part ofthe signal is lost. Also, as long as the transmitted signal is ofconstant magnitude, the total received signal strength is independent ofthe spatial orientation of the field. By detecting phase of thelow-frequency down-converted signals (which are in-phase for incidentlinear polarization) demodulation can be performed.

Assume that the incident electric field vector has a magnitude E₀ and aphase φ. Also assume that the field vector is oriented at an angle θwith respect to one of the receive ports of the dual-port antenna 2100.The magnitude and phase are dependent upon which symbol is beingtransmitted. For example for constant envelope modulation schemes, E₀does not vary over time, but φ varies with the symbol.

Corresponding to an incident field of magnitude E₀, assume the receivedantenna voltage magnitude is V₀. Then, the voltages received at the twoorthogonal ports of the dual-port antenna 2100 are:

V _(port1) =V ₀·cos θ·cos(ω_(RF) t+φ)  (Eq. 28), and

V _(port2) =V ₀·sin θ·cos(ω_(RF) t+φ)  (Eq. 29),

where ω_(RF) is the RF carrier frequency.The down-converted (base-band) signals will then be:

V _(BB,port1) =V ₀·cos θ·cos([ω_(RF)−ω_(LO))t+φ])  (Eq. 30), and

V _(BB,port2) =V ₀·sin θ·cos([ω_(RF)−ω_(LO))t+φ])  (Eq. 31).

Note that the baseband signals are not at DC, but at a low IF frequency,where direct digital phase detection can be performed to estimate φ.Also, note that for linear polarization, received signals at both portsare in-phase but with different amplitudes. Symbol detection can now beperformed by looking at the magnitude and phase of the down-converted IFsignal.

Linear Polarization: Polarization Modulation

In a polarization modulation scheme, the magnitude of the electric fieldvector (E₀), spatial orientation (θ) as well as the phase (φ) can allvary depending on the symbol. A linear polarization modulated inputsignal may be demodulated using the same dual port receiver circuit 2300architecture. Equation 28 through equation 31 again apply, however, notethat unlike the previous case, V₀, θ, as well as φ need to besuccessfully estimated. Note that as before, time-delay/phase can easilybe estimated by digitizing the low frequency base band outputs.

Also, both V₀ as well as θ are determined by the amplitudes of thereceived signals as follows:

V ₀=[(Amp_(BB,port1) ²−Amp_(BB,port2) ²)]^(1/2)  (Eq. 32)

θ=tan⁻¹(Amp_(BB,port2)/Amp_(BB,port1))  (Eq. 33)

Note that for a conventional single-port receiver, two symbols—one at adifferent polarization angle and the other at a different magnitude willappear the same.

Circular Polarization

A circular polarization similarly may be decomposed into two orthogonalcomponents, which, contrary to the linear case, are now in quadrature.Depending on the baseband detection scheme, it is also possible todistinguish between CCW and CW circular polarizations. The descriptionin this section addresses linear polarization demodulating from eitherantenna 1700 referenced in FIG. 17 or antenna 2100 referenced in FIG.21.

Because the two received components are in quadrature, any kind ofquadrature modulation can be directly split into in-phase (I-path) andquadrature-phase (Q-path) components at the antenna 2100 itself withoutthe need for LO phase shifters and additional techniques to minimize IQphase imbalances.

The voltages received at the two ports can be represented as follows:

V _(port1) =V ₀·cos(ω_(RF) t+φ)  (Eq. 34), and

V _(port2) =V ₀·sin(ω_(RF) t+φ)  (Eq. 35),

where ω_(RF) is the RF carrier frequency.

For non-constant envelope modulation, V₀ & φ are symbol dependent,producing:

V _(BB,port1) =V ₀·cos([(ω_(RF)−ω_(LO))t+φ])  (Eq. 36), and

V _(BB,port2) =V ₀·sin([ω_(RF)−ω_(LO))t+φ])  (Eq. 37).

Note that, at the IF frequency, by noting which waveform is leading orlagging, the direction of polarization, i.e. CW or CCW can also bedetected.

Thus, receiving circular polarization incident fields with directin-phase (I) & quadrature-phase (Q) generation at RF through antenna2100 is done using the dual-port antenna based receiver circuit 2300.

FIG. 24 is a simplified block diagram of a basic polarization agiletransmitter circuit 2400, in accordance with an embodiment of thepresent invention. Compared to FIG. 22, FIG. 24 is simplified byremoving the VGAs to depict A₁ and A₂. FIG. 24 shows the basicarchitecture, which allows control of 4 independent variables in thedata stream to generate a 4-D constellation. Basic polarization agilereceiver circuit 2400 includes a first mixer or frequency converter2420, a second mixer 2425, a local oscillator (LO) 2430, a variablephase shifter 2435, and an antenna 2450 to radiate an EM wave E_(t)2455.

An A₁ signal is input to first mixer 2420. An A₂ signal is input tosecond mixer 2425. Local oscillator 2430 is adapted to generate anoscillating signal. Variable phase shifter 2435 is coupled to LO 2430.Variable phase shifter 2435 is adapted to generate a first phase-shiftedoscillating signal and a second phase-shifted oscillating signal. Thefirst phase-shifted oscillating signal and the second phase-shiftedoscillating signal have a phase difference.

Unlike common phase shift circuits which may be set to a fixed phasedifference of 90°, variable phase shifter 2435 is further adapted tovary the phase difference across a predefined range in response to thedata. In other words, the phase difference may be set to any phasedifference in analog fashion—the predefined range set to particularphase differences as discussed in the sections above, for example, toencode data to a polarization angle used as a communication symbol ofthe EM wave 2455. The first mixer 2420 is coupled to variable phaseshifter 2435 and is adapted to convert a frequency of the A₁ signal inresponse to the first phase-shifted oscillating signal to generate afirst frequency converted signal. The second mixer 2425 is coupled tovariable phase shifter 2435 and is adapted to convert a frequency of theA₁ signal in response to the second phase-shifted oscillating signal togenerate a second frequency converted signal.

The outputs of first mixer 2420 and second mixer 2420 may respectivelydrive the first and second antenna ports 2150 and 2170 referenced inFIG. 21 or may respectively drive radiators A and B referenced in FIG.17 above.

As already discussed, the common mode of φ₁ and φ₂ provide the carrierphase and the differential mode provides information about polarization.Assuming unity VGA and PA (or LNA) gains as shown in FIG. 24, theoutputs of the up-conversion mixers are now:

V _(port1) =A ₁·cos(ω₀ t+φ ₁)  (Eq. 38), and

V _(port2) =A ₂·cos(ω₀ t+φ ₂)  (Eq. 39).

These two signals from equations 38 and 39 feed two ports orientedperpendicular in space, i.e. antenna 2100. Each one produces differentlinear polarizations in space. Now, depending on what A₁, A₂, φ₁ and φ₂are, the nature of the polarization in the far-field changes.

The far-field electric field obtained by superposition is given by:

E _(t) =k·A ₁·cos(ω₀ t+φ ₁)u _(x) +k·A ₂·cos(ω₀ t+φ ₂)u _(y)  (Eq. 40),

where k encompasses antenna parameters and is assumed to be constantacross the two polarizations.

Equation 40 re-written in phasor terms produces:

E _(t) =k·A ₁ ·e ^(jω0t) ·e ^(jφ1) ·u _(x) +k·A ₂ ·e ^(jω0t) ·e ^(jφ2)·u _(y)  (Eq. 41).

This provides the four fundamental degrees of freedom for the electricfield. In the most general case, these are defined below.

The electric field in phasor notation is represented by:

E _(t) =e ^(jω0t) ·k·(A ₁ ² ·e ^(j2φ1) +A ₂ ² ·e ^(j2φ2))^(1/2)  (Eq.41),

which contains the magnitude and time-phase of the E-field.

Polarization angle is given by:

angle(E _(t))=tan⁻¹(A ₂ /A ₁)·cos(φ₂−φ₁)  (Eq. 42)

Polarization ratio is given by:

PR=E _(CW) /E _(CCW)=(E _(CWx) +E _(CWy))/(E _(CCWx) +E _(CCWy))  (Eq.43),

where the circular polarization terms can be obtained by resolving thelinear polarizations E_(x) & E_(y) into their respective polarizationcomponents.

The following examples summarize the various polarization modulationembodiments.

Linear polarization is provided when φ₁=φ₂.

Linear polarization modulation is provided when φ₁=φ₂, but A₁ and A₂ aredata dependent.

Circular polarization is provided when φ₁ and φ₂ are 90° apart, andA₁=A₂

Elliptical polarization is provided when φ₁ and φ₂ are an arbitraryangle apart, and A₁ and A₂ are unequal.

The above embodiments of the present invention are illustrative and notlimiting. Various alternatives and equivalents are possible. Although,the invention has been described with reference to certain antennas byway of an example, it is understood that the invention is not limited bythe antenna technology. Other additions, subtractions, or modificationsare obvious in view of the present disclosure and are intended to fallwithin the scope of the appended claims.

What is claimed is:
 1. A method for sending a data from anelectromagnetic radiator by polarization modulation of anelectromagnetic wave, the method comprising: radiating from the radiatora first electromagnetic wave including a first polarization; radiatingfrom the radiator a second electromagnetic wave including a secondpolarization different than the first polarization, the first and secondelectromagnetic waves forming a third electromagnetic wave having athird polarization different from the first or second polarization; andmodulating the third polarization responsive to the data by modulatingone or more parts of the third electromagnetic wave, wherein the data issent in the third polarization.
 2. The method of claim 1, wherein thefirst electromagnetic wave includes a first phase and the secondelectromagnetic wave includes a second phase, wherein the one or moreparts are selected from the group consisting of the first phase, and thesecond phase.
 3. The method of claim 1, wherein the firstelectromagnetic wave includes a first amplitude and the secondelectromagnetic wave includes a second amplitude, wherein the one ormore parts are selected from the group consisting of the firstamplitude, and the second amplitude.
 4. The method of claim 1, whereinthe first electromagnetic wave includes a first phase and a firstamplitude and the second electromagnetic wave includes a second phaseand a second amplitude, wherein the one or more parts are selected fromthe group consisting of the first phase, the second phase, the firstamplitude, and the second amplitude.
 5. The method of claim 1, whereinthe first electromagnetic wave includes a first phase and a firstamplitude and the second electromagnetic wave includes a second phaseand a second amplitude, wherein modulating one or more parts includessimultaneously modulating the first phase, the second phase, the firstamplitude, and the second amplitude.
 6. The method of claim 1 furthercomprising: setting the first polarization to a clock-wise circularpolarization; and setting the second polarization to acounter-clock-wise circular polarization.
 7. The method of claim 1further comprising: setting the first polarization to a first linearpolarization having a first angle; and setting the second polarizationto a second linear polarization having a second angle substantiallyperpendicular to the first angle.
 8. The method of claim 1, wherein thethird polarization is a linear polarization.
 9. The method of claim 1,wherein the third polarization is an elliptical polarization.
 10. Themethod of claim 1 further comprising: setting a first amplitude of thefirst electromagnetic wave equal to a second amplitude of the secondelectromagnetic wave; setting the first polarization to a clock-wisecircular polarization; setting the second polarization to acounter-clock-wise circular polarization, wherein the one or more partsincludes a first phase of the first electromagnetic wave and a secondphase of the second electromagnetic wave, the third polarization being alinear polarization having an angle; and modulating the angle responsiveto a difference between the first and second phase, the difference beingresponsive to the data.
 11. The method of claim 10, wherein the anglecorresponds to a symbol representing the data.
 12. The method of claim10, wherein the symbol sends a single bit of information at a time. 13.The method of claim 10, wherein the symbol sends a plurality of bits ofdata simultaneously in time.
 14. The method of claim 1 furthercomprising: setting a first phase of the first electromagnetic waveequal to a second phase of the second electromagnetic wave; setting thefirst polarization to a clock-wise circular polarization; setting thesecond polarization to a counter-clock-wise circular polarization,wherein the one or more parts includes a first amplitude of the firstelectromagnetic wave and a second amplitude of the secondelectromagnetic wave, the third polarization being an ellipticalpolarization having a polarization ratio; and modulating thepolarization ratio responsive to the data.
 15. The method of claim 14,wherein the polarization ratio is a quotient of the first amplitudedivided by the second amplitude.
 16. The method of claim 14, wherein thepolarization ratio corresponds to a symbol representing the data. 17.The method of claim 16, wherein the symbol sends a single bit ofinformation at a time.
 18. The method of claim 16, wherein the symbolsends a plurality of bits of data simultaneously in time.
 19. A methodfor receiving a data from an electromagnetic receiver by polarizationdemodulation of an electromagnetic wave, the method comprising:receiving from an antenna a first signal having a first polarization anda second signal having a second polarization, the first and secondsignals being associated with the electromagnetic wave, theelectromagnetic wave including a third polarization; determining anamplitude of the first signal; determining an amplitude of the secondsignal; and determining an angle of the third polarization to receivethe data.
 20. The method of claim 19, wherein the first and secondpolarizations are linear.
 21. The method of claim 20, wherein the firstand second polarizations are substantially orthogonal.
 22. The method ofclaim 19, wherein determining the angle includes calculating a quotientof the amplitude of the second signal divided by the amplitude of thefirst signal.
 23. A system for sending a data from a radiator bypolarization modulation of an electromagnetic wave comprising: anoscillator adapted to generate an oscillating signal; and a phaseshifter coupled to the oscillator and adapted to generate a firstphase-shifted oscillating signal having a first phase, wherein a phasedifference exists between the first phase and the oscillating signal,wherein the phase shifter is further adapted to vary the phasedifference across a predefined range in response to the data.
 24. Thesystem of claim 23, wherein the phase shifter is further adapted togenerate a second phase-shifted oscillating signal having a secondphase, wherein a phase difference between the first phase and the secondphase defines the phase difference.
 25. The system of claim 23 furthercomprising a radiator adapted to accept the first phase-shiftedoscillating signal and the oscillating signal and respectively radiate afirst electromagnetic wave having a first circular polarization and asecond electromagnetic wave having a second circular polarizationdifferent than the first circular polarization, the firstelectromagnetic wave and the second electromagnetic wave adapted to forma third electromagnetic wave having linear polarization and having anangle, the angle being responsive to the data.
 26. The system of claim25, wherein the radiator includes an antenna positioned substantially ina plane defined by a first direction and a second direction orthogonalto the first direction, the antenna being symmetric about a center inthe first direction and in the second direction, the antenna including afirst port positioned at an edge of the antenna in the first directionand a second port positioned at an edge of the antenna in the seconddirection.
 27. The system of claim 25, wherein the radiator includes afirst antenna adapted to radiate the first electromagnetic wave andsecond antenna adapted to radiate the second electromagnetic wave. 28.The system of claim 25, wherein the angle corresponds to a symbolrepresenting the data.
 29. The system of claim 28, wherein the symbolsends a single bit of information at a time.
 30. The system of claim 28,wherein the symbol sends a plurality of bits of data simultaneously intime.
 31. A system for sending a data from a radiator by polarizationmodulation of an electromagnetic wave comprising: a first circuitadapted to generate a first signal and a second signal; an oscillatoradapted to generate an oscillating signal; a phase shifter coupled tothe oscillator and adapted to generate a first phase-shifted oscillatingsignal and a second phase-shifted oscillating signal having a phasedifference therebetween, wherein the phase shifter is adapted to varythe phase difference across a predefined range in response to the data;a first frequency converter coupled to the phase shifter and the firstcircuit, the first frequency converter adapted to convert a frequency ofthe first signal in response to the first phase-shifted oscillatingsignal to generate a first frequency converted signal; and a secondfrequency converter coupled to the phase shifter and the first circuit,the second frequency converter adapted to convert a frequency of thesecond signal in response to the second phase-shifted oscillating signalto generate a second frequency converted signal.
 32. The system of claim31 further comprising a radiator adapted to accept the first and secondfrequency converted signals and respectively radiate a firstelectromagnetic wave having a first polarization and a secondelectromagnetic wave having a second polarization different than thefirst polarization, the first electromagnetic wave and the secondelectromagnetic wave adapted to form a third electromagnetic wave havinga third polarization, the third polarization modulated by one or moreparts of the combined electromagnetic wave responsive to the data. 33.The system of claim 32, wherein the first electromagnetic wave includesa first phase and the second electromagnetic wave includes a secondphase, wherein the one or more parts are selected from the groupconsisting of the first phase, and the second phase.
 34. The system ofclaim 32, wherein the first electromagnetic wave includes a firstamplitude and the second electromagnetic wave includes a secondamplitude, wherein the one or more parts are selected from the groupconsisting of the first amplitude, and the second amplitude.
 35. Thesystem of claim 32, wherein the first electromagnetic wave includes afirst phase and a first amplitude and the second electromagnetic waveincludes a second phase and a second amplitude, wherein the one or moreparts are selected from the group consisting of the first phase, thesecond phase, the first amplitude, and the second amplitude.
 36. Thesystem of claim 32, wherein the first electromagnetic wave includes afirst phase and a first amplitude and the second electromagnetic waveincludes a second phase and a second amplitude, wherein modulating oneor more parts includes simultaneously modulating the first phase, thesecond phase, the first amplitude, and the second amplitude.
 37. Thesystem of claim 32, wherein the radiator includes an antenna positionedsubstantially in a plane defined by a first direction and a seconddirection orthogonal to the first direction, the antenna being symmetricabout a center in the first direction and in the second direction, theantenna including a first port positioned at an edge of the antenna inthe first direction and a second port positioned at an edge of theantenna in the second direction.
 38. The system of claim 32, wherein theradiator includes a first antenna adapted to radiate the firstelectromagnetic wave and second antenna adapted to radiate the secondelectromagnetic wave.
 39. The system of claim 32, wherein the firstpolarization is a clock-wise circular polarization and the secondpolarization is a counter-clock-wise circular polarization.
 40. Thesystem of claim 32, wherein the first polarization is a first linearpolarization having a first angle and the second polarization is asecond linear polarization having a second angle substantiallyperpendicular to the first angle.
 41. The system of claim 32, whereinthe third polarization is a linear polarization.
 42. The system of claim32, wherein the third polarization is an elliptical polarization. 43.The system of claim 32, wherein a first phase of the firstelectromagnetic wave is equal to a second phase of the secondelectromagnetic wave, the first polarization is a clock-wise circularpolarization, the second polarization is a counter-clock-wise circularpolarization, wherein the one or more parts includes a first amplitudeof the first electromagnetic wave and a second amplitude of the secondelectromagnetic wave, the third polarization being an ellipticalpolarization having a polarization ratio responsive to the data.
 44. Thesystem of claim 43, wherein the polarization ratio is a quotient of thefirst amplitude divided by the second amplitude.
 45. The system of claim43, wherein the polarization ratio corresponds to a symbol representingthe data.
 46. The system of claim 45, wherein the symbol sends a singlebit of information at a time.
 47. The system of claim 45, wherein thesymbol sends a plurality of bits of data simultaneously in time.
 48. Asystem for receiving a data from an electromagnetic wave by polarizationdemodulation comprising: an antenna adapted to pick up a first signalhaving a first polarization and a second signal having a secondpolarization, the first and second signals being associated with theelectromagnetic wave, the electromagnetic wave including a thirdpolarization; a first circuit adapted to determine an amplitude of thefirst signal; a second circuit adapted to determine an amplitude of thesecond signal; and a third circuit adapted to determine an angle of thethird polarization responsive to the data.
 49. The system of claim 48,wherein the first and second polarizations are linear.
 50. The system ofclaim 49, wherein the first and second polarizations are substantiallyorthogonal.
 51. The system of claim 48, wherein the third circuit isfurther adapted to calculate a quotient of the amplitude of the secondsignal divided by the amplitude of the first signal, wherein thequotient is responsive to the angle.